Study the immune mechanisms whereby cells of the intestinal tract of swine are protected against enteric viral infections. Determine the role(s) of the major classes of immunoglobulins (IgM, IgA, IgG) in virus neutralization and protection of intestinal epithelium. Investigate the passive immunity against virulent transmissible gastroenteritis (TGE) virus infection obtained by newborn pigs nursing sows immunized by various routes with attenuated and virulent TGE viruses. Determine the effect(s) of virulent and attentuated TGE viruses on the intestinal epithelium of newborn pigs nursing non-immune sows; compare these results to those obtained from newborn pigs receiving IgA (sow orally immunized with virulent virus) or IgG (sow intramuscularly immunized with attentuated virus) anti-TGE antibodies. Study the serum and secretory immune response in neonatal and adult swine following exposure to TGE virus. Determine the source(s) of IgA anti-TGE antibodies in the milk of immune sows.